title: Effect of hourly concentration of particulate matter on peak expiratory flow in hospitalized children: a panel study.
abstract: BACKGROUND
  Little information is available on the possible association between hourly short-term air pollution and peak expiratory flow (PEF) in asthmatic children.
  
  
  METHODS
  PEF was measured twice daily, from October through December, 2000, in 17 children aged 8 to 15 years hospitalized with severe asthma. A total of 1198 PEF measurements were made at 7 a.m. and 1175 at 7 p.m. Measurements were conducted immediately prior to medication under the guidance of trained nurses. PEF changes were estimated in 10-μg/m3 increments of particulate matter with a 50% cut-off aerodynamic diameter of ≤2.5 μm (PM2.5), with adjustment for sex, age, height, and temperature. Lagged-hour exposures of up to 24 hours were examined.
  
  
  RESULTS
  Increased 24-hour mean concentration of PM2.5 was associated with a decrease in both morning and evening PEF (-3.0 l/minute; 95%CI: -4.6, -1.4 and -4.4 l/minute; 95%CI: -7.1, -1.7, respectively). In addition, hourly concentrations of PM2.5 and PEF showed a significant association between some lags of PM2.5 and PEF. Effect size was almost -3 l/minute in both morning and evening PEF for an hourly PM2.5 concentration of 10 μg/m3 in several lags. Even after adjustment for other air pollutants, some of the significant associations with PEF remained.
  
  
  CONCLUSIONS
  Among hospitalized children with severe asthma, increased hourly concentration of PM2.5 was associated with a decrease in PEF.
authors.affiliation: Department of Epidemiology and Healthcare Research, Kyoto University School of Public Health, Yoshidakonoe-cho, Sakyo-ku, Kyoto, Japan. yamazaki.shin@kt8.ecs.kyoto-u.ac.jp
authors.forename: Shin
authors.initials: S
authors.lastname: Yamazaki
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shima
authors.forename: Michiko
authors.initials: M
authors.lastname: Ando
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nitta
authors.forename: Hiroko
authors.initials: H
authors.lastname: Watanabe
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nishimuta
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000633:toxicity*; D001249:Asthma / Q000503:physiopathology*; D002648:Child; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D019570:Inhalation Exposure; D007564:Japan; D008297:Male; D052638:Particulate Matter / Q000633:toxicity*; D010366:Peak Expiratory Flow Rate / Q000187:drug effects*; D013147:Spirometry / Q000295:instrumentation
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter